Recently, the general trends in designing electronic devices are toward high density, high performance, small size, light weightiness and portability. With the increasing development of electronic industries, the internal circuitries of the electronic devices are gradually modularized. In other words, plural electronic components are integrated into a single circuit module. For example, a power module is one of the widely-used circuit modules. An example of the power module includes a DC-to-DC converter, a DC-to-AC converter, an AC-to-DC converter, or the like. After the electronic components (e.g. capacitors, resistors, inductors, transformers, diodes and transistors) are integrated as a power module, the power module may be installed on a system circuit board.
An intelligent power module (IPM) is widely used in an intelligent motor driving circuit of an electrical appliance or an industrial appliance. In a conventional package structure of the intelligent power module, electronic components are supported by a lead frame and packaged by an encapsulation material. However, the process of fabricating this package structure is complicated. Moreover, the heat-dissipating efficiency of the package structure is usually insufficient, and the package structure is readily broken. In another conventional package structure of the intelligent power module, a printed circuit board with electronic components is directly disposed within a case, and covered by a covering member. Moreover, the case and the covering member are combined together via an adhesive. However, this package structure still has some drawbacks. For example, since the covering member cannot be securely fixed on the case through the adhesive. Moreover, when the package structure is combined with other device such as a heat sink, the bottom side of the case is easily suffered from bending and deformation because of the stress transmitted from the device. Since the package structure cannot be in close contact with the heat sink, the heat-dissipating efficiency is impaired, or even the package structure is detached from the heat sink. Under this circumstance, the use of the power module is not safe.
Therefore, there is a need of providing an improved package structure in order to overcome the above drawbacks.